1. Field of Invention
The present invention relates to a display method of a display device, and more particularly to a display method of an electrophoresis display (EPD) device.
2. Related Art
An EPD device is a novel display device recently developed in the field of displaying technology, and is currently mostly applied to electronic papers (e-papers), electronic books, electronic billboards, and electronic tags. The EPD device is a reflective display device, that is, the EPD device presents images by using the reflection of light. Therefore, compared with the commonly used thin-film transistor liquid crystal displays (TFT LCDs), the EPD device displays images without using any backlight sources.
FIG. 1A is a schematic cross-sectional view of a conventional EPD device. Referring to FIG. 1A, a conventional EPD device 100 has a plurality of pixels (not shown), and includes an electrophoretic solution 110, a plurality of charged particles 120, a plurality of common electrodes 130 (only one is shown in FIG. 1A), a plurality of pixel electrodes 140 (only one is shown in FIG. 1A), and a plurality of transistors (not shown). The pixel electrodes 140 are generally integrated with the transistors to form an active component array substrate, which substantially has the same structure as a TFT array substrate of the current TFT LCD.
Both the electrophoretic solution 110 and the charged particles 120 are located between the common electrodes 130 and the pixel electrodes 140, and the charged particles 120 are distributed in the electrophoretic solution 110. The net charge of each charged particle 120 is not equal to zero, and is positive or negative. In other words, the charged particles 120 are particles with positive or negative charges, rather than neutral particles.
When a voltage is applied to the pixel electrode 140, an electric field is generated between the pixel electrode 140 and the common electrode 130, and upon being driven by the electric field, the charged particles 120 start to move. In detail, when the charged particles 120 are all with positive charges, and a positive voltage is applied to the pixel electrode 140, the charged particles 120 move towards the common electrode 130. When the charged particles 120 are all with positive charges, and a negative voltage is applied to the pixel electrode 140, the charged particles 120 move towards the pixel electrode 140.
The EPD device 100 generally displays an image at the common electrode 130, so that a user usually views the image from the common electrode 130. In a certain pixel of the EPD device 100, the closer the charged particles 120 approach the common electrode 130, the color presented by the pixel will be more similar to the color of the charged particles 120; on the contrary, the further the charged particles 120 move away from the common electrode 130, the color presented by the pixel will be more similar to the color of the electrophoretic solution 110. By changing the voltage applied to the pixel electrode 140, the distance between the charged particles 120 and the common electrode 130 can be adjusted, so as to enable the pixels of the EPD device 100 to display colors with different gray levels.
In addition, when the EPD device 100 is in a power-off or low-power state, the overall distance between the charged particles 120 and the common electrode 130 is not changed, so that the image displayed by the EPD device 100 remains and does not disappear. Once the image needs to be refreshed, the distance between the charged particles 120 and the common electrode 130 is changed. Therefore, the EPD device 100 has an image memory capability.
FIG. 1B is a voltage timing chart when the EPD device in FIG. 1A is driven. Referring to FIGS. 1A and 1B, when the EPD device 100 refreshes the image, firstly, a reset time R1 is required and passed. During the reset time R1, the pixel electrode 140 receives a reset voltage Vr, such that all of the charged particles 120 are enabled to move to the same position, for example, all of the charged particles 120 move to the common electrode 130 or the pixel electrode 140.
After the reset time R1 elapsed, a data write time W1 is passed, and the pixel electrode 140 receives a write voltage Vw1 to adjust the distance between the charged particles 120 and the common electrode 130, so as to display colors with different gray levels. Since all of the charged particles 120 have moved to the same position (generally at the common electrodes 130 or the pixel electrodes 140) under the influence of the reset voltage Vr before the write voltage Vw1 is received, the pixels can display colors with correct gray levels only when the pixel electrode 140 receives the write voltage Vw1, such that the image of the EPD device 100 is not distorted.
However, under the influence of the reset time R1, the EPD device 100 has to spend much time on refreshing the image, thereby resulting in a low image refresh rate of the EPD device 100.